Process of making dry cells



30, 9 w. D. STALEY 1,874,375

PROCESS OF MAKING DRY CELLS Original Filed July 6, 1928 l a a 9 /0 alga z. -l-;;;;;:-- Q

INVENTOR fl dfflffl ffa/e .HATTORNELYS' improvement over the Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE warm: 1). sunny or momma, rumors, xssrenoa TO BURGESS 3m courm, or uanrson, WISCONSIN, A coarona'rrou or wrsconsm rnocass or MAKING nax ems Original application filed July 6, 1928, Serial No. 290,761. Patent No. 1,700,090, dated Kay 27, 1980.

Divided and this application filed This invention relates to a coated dry cell depolarizing core and more specifically to the method of formin thegelatinous electrolyte in a dry cell of t e pasted type and is an roduct and method disclosed in Schorger atent Nos. 1,316,597 and 1,370,052.

The obj ect of this invention is to provide an improved method of forming the gelatinous electrolyte in a dry cell of the pasted type and to provide a method for making a reserve type of cell.

In the accompanying drawing,

Fig. 1 is a vertical sectional view of a cell; and a Fig. 2 is a similar view of a reserve cell prior to the .addition of the electrolyte.

A dry cellof the pasted type usually has the construction shown in cross section in.

Fig. 1. A depolarizing core is made of a central carbon rod 1, with a metalliocap 2, around which is molded a moist depolarizing mixture 3 of powdered graphite, a depolarizer such as manganese dioxide, and conducting salts such as ammonium chloride and zinc chloride. The depolarizing core may be wrapped in a bibulous wrapper such as cheesecloth but in the cell of my invention this wrapping is unnecessary. The core is separated from the zinc can 5 by a pasty electrolyte 6 which consists of a mixture of a gelatinized' cereal such as flour or starch, zinc and ammonium chlorides, and water. The bottom of the depolarizing core may be insulated from the can by means of insulating wax or by an insulating washer 7. The cell is completed by sealing material 8 resting on. a spaced insulating washer 9 thereby providing expansion space 10. W

This invention relates specificallyfto the method of producing the gelatinous -electrolyte 6 whereb the bibulous wrapper may be eliminated. uch a aste electrolyte is now formed in several di erent ways. The. space between the core and can may be filled with a fluid suspension of cereal and water containing some of the electrolyte salts and the can then immersed in hot water to gelatinize the cereal. V In another method, as described in Ham- J'uly 11, 1929. Serial No. 377,474.

buechen Patent No. 1,292,764 the cereal, such as corn starch, or a mixture of corn starch and corn meal, is stirred rapidly into a strong solution of ammonium chloride and zinc chloride, the percentage of the zinc chloride being high enough to gelatinize the cereal within a few minutes after mixing, thus allowing enough time to pour the suspension of cereal into the space between the core and zinc can before gelatinization occurs.

This method is modified in Schulte Patent N 0. 1,37 0,056 in which the cereal is suspended in a water solution of ammoniumchloride and weak zinc chloride of, such strength that it does not gelatinize the cereal. A second solution of strong zinc chloride and ammonium chloride is added to the starch suspension in such quantity as to give a final mixture of about the same composition as specified in Patent No. 1,292,764; diately introduced into the zinc cup containing the depolarizing core and the cereal gelatinizes within a few minutes as previously described. This inethod is more practical as two solutions are mixed which permits the use of simplified machinery for the operation.

If the gelatinizable electrolyte is introduced into the zinc cup by mechanical means as bylthe apparatus described in Hodge Patent the final electrolyte as it is introduced into the electrolyte hopper of thatapparatus to keep it liquid as long as possible and thereby preyent gelatinization in the hopper before it s lntroduced into the zinc cup. However, if'the apparatus is closed down for a few The mixture is imme- 0. 1,669,054, then it is best to compound minutes, gelatinization may take place and the electrolyte must be drained'from the apparatus. With the present invention these difficultiesare overcome as the gelatinizing cereal is in the form of a coating on the depolarizing core and the strong chloride gelatinizing solution free from cereal is the only solution used in the hopper. This solution, since cereal is not present, does not gelatinize and maybe kept in the hopper indefinitely. I

In-carrvi ng out my invention I use a liquid suspension of ungelatinized starch in a water solution of a colloid, such as gelatinized of this salt starch, such as is described and claimed in the copendin application Serial No. 290,885 of my cowor er, W. B. Schulte'. The depolarizing core is dipped into this magma, allowed to set and then inserted into a zinc can containing an electrolyte containing zinc chloride. The zinc chloride slowly gelatinizes and swells the cereal coating so that the space I a suitable colloid suspending medium for the ungelatinized starch or cereal; I use in this specification the word starch as a generic term which includes all kinds of starches, meals,-and .flours which gelatinize in hot water or in the presence of strong zinc chloride but not in cold water. Without the presence of the colloid in the water the ungelatinized starch grains, which are to be suspended therein, settle rapidly to the bottom. Furthermore, a binder is lacking so that any coating formed with such starch dries to such a condition that it has little strength, and is not coherent.

A liquid colloid suspending medium may be made by making a dilute solution (being liq- Rid at room temperatures) of glue or gelat inized starch in water, gelatinized starch being preferred. The amount of starch which is in gelatinized form may vary from 0.5% to 1.5% of the final complete suspension. The starch is gelatinized preferably by heating in water. After cooling, the -unelatinized raw starch is stirred into the coloid containing ,suspending'medium so that the final suspension contains from to of starch. This suspension is mobile and liquid which distinguishes it from a paste? whlch is not mobile.

The viscosity of the suspending medium may be cut down or the amount of starch which may be suspended may be increased by dissolving ammonium chloride in the suspending medium. Since ammonium chloride is needed in the'gelatinous electrolyte of a dry cell the addition of the ammonium chloride to the starch suspension accomplishes a double purpose. From 5% to 15% preferably is present in the suspension. The depolarizing core is dipped into this suspension and preferably is withdrawn slowly therefrom, the entire operation reguiring from 5 to 15 seconds. The slow withrawalresults ina more even coating which does not have much tendency to form a bead at the bottom. The coating may vary from almost nothing up to about A in thickness depending upon the space available' between the core and zinc can in the resulting dry cell. The consistency of the suspension may bevaried according to the thickness required. The coatin on the core sets rapidly as the moisture o the coating soaks into the depolarizing mix and it may be handled within a few minutes. It is almost completely dry coating and the zinc can. The starch slowly gelatinizes and swells as the zinc chloride solution soaks into it so that it gradually forms a solid paste 6 between the core 3 and can 5. This action is usually complete enough to allow handling of the cells within several hours. However, the action may be finished Within a few minutes by immersing the cans in hot water. The core does not soften by this method as the moisture in the electrolyte does not. come directly in contact with the core which is protected by the starch and colloid bound coating. The coating on the core also serves to keep the core centered in the can before introducing the gelatinizing electrolyte.

If the core is dipped in the starch suspension as described the bottom of the core is coated also with the mixture of starch and binder. It usually is desirable to have the bottom of the core insulated from the bottom of the can to prevent any possibility of short circuiting. This may be accomplished byinserting an insulating washer at the bottom of the can but I- prefer to coat the bottom of the core, prior to coating with the starch, with an insulating material such as nitrocellulose,pitcjh, asphalt, or a wax such as beeswax, paralfin or sealing wax. When a wax. is used to insulate the bottom of the core it has a further advantage in that the starch dip does not adhere to it. Therefore the bottom of the core is free of starch. If a small amount should adhere it is easily removed by setting the core on an absorbent P vWhen a core is dip ed into the starch suspension the coating epends in some degree upon the .rate at which the water is absorbed from the starch coating by the depolarizing mix. The density of the core and its.

moisture content determines its water absorbing ca acity. Furthermore, if too much coating. This variation may be overcome by first coating the core with a thin colloid coating such as glue, agar-agar, boiled starch, and the like. A 4% agar-agar solution in water makes an excellent dip which is preferably used at a temperature of about 60 C. A thin film of agarar is formed on the core. The starch coating'is put on over theagar-agar coating. A much more uniform starch coating is thus obtained which is not as heavy for the same starch sus nsion, as when the bare core is coated. he starch coating sets moreslowly due to the slower absorption of moisture. by the core. The

bottom of the core preferably is coated. with wax before the agar-agar coating is applied:

After the coating has dried it contains from 1% to 4% of gelatinized starch, and if ammonium chloride is used in the dip, from 10% to 40% of that salt.

As a specific embodiment of my invention the following illustration will serve to guide those skilled in the art. starch suspension is made up which contains the following'inredients 44.2% water, 0.7% boiled starch,

11.7% ammonium chloride,'and,43.4'% raw commercial corn starch. The core bottom is coated with insulating wax after which it is dipped into and slowly' withdrawn from the above suspension and set on any absorbent pad. After settingfor several. minutes it is introduced into a zinc can containing an electrolyte of the following composition: 38.7% 21101., 36.8% H O, 24.5% NILCI.

5 The cell is washered and pitched and allowed to stand for several hours after which it may be handled. Within several days the flash and voltage of the cell become normal indicating the com letion of the diffusion of the 40 electrolyte an gelatinization of the starch.

The cell may be set in water at 75 C. for several minutes after itching when it will be ready to put in service shortly thereafter.

This method of introducing the starch into and then gelatinizing it in a dry cell lends itselfto the manufacture of a reserve or delayed action type of cell. The coated core is introduced into the can but without the liquid gelatinizing electrol te. The cell is top sealedin the usual way ut with or witha out provlsion' for introducing the liquid electrolyte when it is desired to put the cell into action. This may be accomplished preferably by pouring the gelatinizing liquid into a hole 11 left in the seal 8 and washer '9, or if such hole has not been provided it may be easily made by means of a drill or-a hot iron. The electrolyte is poured into the space he'- tween the core and can, the hole is rescaled,

and the cell is then allowed to remain quiet for several hours and it is readyfor use. The 'cell 'can be put into immediate use by immersing it in hot water for several minutes. The can and core aufier no appreciable deterioration prior to the introduction. of the electrolyte.

The starch coating described herein may also be used to coat other shapes of depolarizing cores than the cylindrical type which has been illustrated. It even may be used to coat flat depolarizing mix cakes or cores on those surfaces adiacent the zinc anode. The gelatinizing zinc chloride may be incorporated in the mix cake underthose conditions. A small amount of zinc chloride insulficient to elatinize the cereal, may also be incorporatef in the liquid suspension.

I have also found that potato starch may be used to displace the ungelatini'zed' corn starch of the liquid suspension partially or entirely. The potato starch gelatinizes rapnization of thecoating on the core when the cell is assembled as described, the gelatinization taking place in twenty to thirty minutes instead of several hours withoutimmersing the cell in hot water The advantage of the potato starch is apparent therefore to those skilled in the art.

Throughout this cification the sequence of-operations where y'the liquidelectrolyte is introduced into the can may be either 'of the following: either {firstQputting the core into the can'and then ouring in the electrolyte, or first pouring t e electrolyte into the can and then inserting the core. I do not wish to limit this specification to either of these two methods. This application is a division of m copending application, serial No. 290,761, led Jul 6,1928 (now Patent No. 1,760,090, grante May 27, 1930). The claims of that application are directed to the product herein disclosed and the claims of cylindrical a said core with a waxy substance, making asuspension of starch in a li uid solution of a suitable colloid in water, an applying a coating of said suspension to and core.

2. The method of coating a cylindrical drK cell cathode core with gelatinizable starc which comprises dipping the bottom of said ,7

core into a waxy substance to insulate the bottom of said core, and then making a suspension of 35% to 50% of starch in a liquid solution of gelatinized starch, and applying a coating of said suspension to said core.

3. The method of coatinpi a cylindrical d i cell cathode core with whiclicomprises insulatm the bottom of said core'w ith a wa substance, making a suspension of starch in a liquid solution of gelatinized starch, applying a coating of said atinizable stare 1 no tinizable start il i suspension to said core, and allowing said coating to set.

4. The method of coating 2. dry cell core.

with gelatinizablestarch which comprises dipping said core into a liquid solution of a suitable colloid to form a. thin coating of said colloid on said core, allowing said coating to set, making a suspension of starch in a liquid solution of gelatinized starch and applying a coating-of said su ension to said core.

5. The method 0 coating a cylindrical dry cell cathode core with gelatinizable starch which comprises insulating the bottom of said core with a suitable waxy substance, dipping said core into a liquid solution of ,agaragar to form a thin coating thereon, allowing said coating to set making a suspension of starch in a liquid solution of gelatinized starch, applying a'coating of said suspension to said core and allowingsaid coating to set.

'6. The method of dry cell manufacture which consists in forming about a carbon rod a moist, active mixture of carbonaceous material and depolarizer to form a fragile dry cell cathode core, applying a coating of starch in a liquid solution of gelatinized starch to said core, introducing said coated core into azinc can and pouring a gelatinizing electrolyte about said core. a

7. The method of dry cell manufacture which consists in forming about a carbon rod a moist, active mixture of carbonaceous material and depolarizer to form a fragile dry cell cathode core, dipping said core into a suitable molten insulating wax to coat the bottom of said core, applying a coating of starch in a liquid solution of ge'laitinized starch to said core, allowing said coating to set, introducing said coated core into a zinc can, pouring agelatinizing electrolyte about said core, and immersing said can in hot water to hasten the gelatinization of the starch in the coating on said core.

In testimony whereof I afiix my signature.

WAYNE D. STALEY. 

